This invention relates to a process for the extraction of open coffee cartridges, to a coffee cartridge and to an extraction device for carrying out the process.
More particularly, the invention relates to the extraction of a roasted and ground coffee contained in a cartridge substantially frustoconical in shape by the injection of hot water under pressure.
There are several reasons for the use of coffee cartridges, above all in the field of espresso type coffees which are extracted under pressure, namely: hygiene, optimal storage of the coffee, ease of use, better control of the quality of the coffee obtained and better reproducibility of the extraction conditions.
Sealed cartridges which open under the pressure of the water injected satisfy these requirements.
EP 292 556, example, relates to cartridges which have weakened zones that tear preferentially under the effect of pressure.
This solution has the disadvantage of increasing the complexity and price of the cartridge because the materials used have to be treated very precisely to ensure that the cartridges open correctly and reproducibly.
EP 242 556 also describes an extraction device using cartridges of the above type and comprising a hollow cylindrical body having an internal shape substantially corresponding to the external shape of the cartridge to be extracted, the body comprising an injector at its upper end following the axis of the cylinder and, on its outer part, a spring retaining a ring for releasing the cartridge on completion of extraction. A device such as this enables a coffee of high quality to be obtained, but can only be used with a single type and shape of cartridge perfectly adaptable to the internal shape of the hollow cylinder.